Calculate the pressure of the following mixture.

[marcoskids]

Homework Statement

An oil reservoir contains at water/oil contact (WOC) of 12000ft contains a water column at 800ft, oil at 500ft and gas at 600ft height

Calculate the pressure at WOC, 12500, 11700 and 11000 ft?

Homework Equations

P = rho g h + Patm

1 ft = 0.305m
Rho water = 1000
Rho Oil = 800
Rho gas = 120

The Attempt at a Solution

P WOC = 1000*9.81*(12000*0.305) + 800*9.81*(12000*0.305)+patm = 64.7Mpa

For the water column for example would the pressure be:

Pwoc + (1000*9.81*(800*0.305) = 67.1Mpa ?
or
Pwoc + (1000*9.81*((12000-800)*0.305)) = 98.2Mpa
or
Pwoc+(1000*9.81*((12000+800)*0.305)) = 102.3Mpa

Basically what height do I have to use?

And what densitys do I need to use for the depths at 12000, 11700 and 11000ft please?

 

[marcoskids]

New approach does this look better?

Pwoc = (rhoWgh ) + (rhoOgh)
= (1000*9.8*(12000*0.305)) + (800*9.8*(12000*0.305)
= 64.6 Mpa

Pgoc = (rhoG gh) + (rhoO gh)
= ((120*9.8*((12000-800)*0.305))) + (800*9.8*((12000-800)*0.305)))
= 30.8 Mpa

P12500 = (rhoW gh)
= 1000*9.8*(12500*0.305)
= 34.7 Mpa